linux-kernel - Re: [PATCH] mm, thp: display [never] for defrag when THP is set to never

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Date: Fri, 23 Feb 2024 19:01:58 +0800
From: Liu Song <liusong@...ux.alibaba.com>
To: David Hildenbrand <david@...hat.com>,
 Yuanhe Shu <xiangzao@...ux.alibaba.com>, akpm@...ux-foundation.org
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm, thp: display [never] for defrag when THP is set to
 never


在 2024/2/22 20:14, David Hildenbrand 写道:
> On 22.02.24 12:53, Yuanhe Shu wrote:
>> When transparent_hugepage is set to never by cmdline or echo, defrag
>> still show what it used to be and can be modified which makes user
>> confusing whether defrag would take effect.
>>
>> Actually if transparent_hugepage is set to never, defrag will not take
>> effect. Just Display never and remain unchangeable to for defrag when
>> transparent_hugepage is set to never.
>>
>> Suggested-by: Liu Song <liusong@...ux.alibaba.com>
>> Signed-off-by: Yuanhe Shu <xiangzao@...ux.alibaba.com>
>> ---
>
> No, I don't think we want such a dependency between both options.
>
> You might just end up breaking existing scripts (enable defrag before 
> enabling THP) for no good reason.
>
In certain situations where khugepaged_thread is NULL, it would be more
reasonable for the value of
/sys/kernel/mm/transparent_hugepage/khugepaged/defrag to be 0. The patch
should include a fix for this case.

Thanks